1. Technical Field
The present invention relates to a printing technique for printing image data which represent a predetermined image, and more particularly relates to a technique for generating dot data which indicate the presence or absence of dot formation.
2. Background Technology
Dithering and error diffusion are widely known as techniques (hereinafter referred to as halftone techniques) for expressing the gradations of an image by an expression method having fewer gradations than the original image. Since dithering and error diffusion each have advantages and disadvantages, there has been a need for halftone processing which combines dithering-type factors and error diffusion method elements. For example, Patent Citations 1 and 2 below disclose techniques of halftone processing in which dithering-type factors and error diffusion method elements are combined by using a dither mask of an ordered dithering method on the error diffusion threshold value to periodically vary the threshold value.
However, in the techniques of Patent Citations 1 and 2, the degree to which dithering-type factors and error diffusion method elements contribute is difficult to control according to the characteristics of the print image data that are to be subjected to halftone processing.
Japanese Laid-open Patent Publication No. 2001-292320 (Patent Document 1), Japanese Laid-open Patent Publication No. 2003-234893 (Patent Document 2), Japanese Laid-open Patent Publication No. 2006-140579 (Patent Document 3) and Japanese Laid-open Patent Publication No. 2006-67347 (Patent Document 2) are examples of the related art.